RO, DI, and Discus

Darn.  I KNEW I should have put a <ggggg> in my one liner on "who in their
right mind would fill their tank with DI water."  Oh, well.  It was pretty
late at night and I was feeling ornery.  It struck me as a really DUMB
question, so I gave a far too simple and caustic answer to what seemed like
an oversimplified question.  Sorry!  :-(

I spend quite a bit of time on the Discus list, and water is definitely a hot

There was quite a long thread recently about DI vs. RO water.  Some folks use
DI, then run that through RO, to "save the membrane."  Others run RO water
through a DI column or a pair of columns, one Cation Exchange, the other
Anion Exchange.  BREEDERS of Discus will often "fill the tank" of the
BREEDING PAIR with DI water.  The eggs are extremely sensitive to residual
minerals and other substances, also pH.  (BTW, the tank, with a pair of
8"-10" diameter pair of Discus, will NOT stay at the pure DI - equivalent of
distilled - state for more than perhaps a few seconds.) Raising the young Disc
us is quite a different story, as is keeping pairs or groups of adults around
that you are not trying to breed.  As Karen Randall said, lots of BIG water
changes are used, and it is often just tap water.  Only the breeding tank is
critical, and yes, I do know Discus breeders that DO use DI water in those
tanks.  In general, they are the ones who have really atrocious water at the

I hereby sentence myself to forty lashes with a strand of Java Moss for being
unnecessarily caustic on the List.  As I said, it was late at night.  1:45 in
the morning, to be exact!  Sorry again.  :-(